The present invention relates to a microscopic structure having a size of about several microns to several hundred microns.
For producing the microscopic structure, a LIGA (Lithographie, Galvanoformung, Abformung) process which is being developed in Germany is known. FIGS. 1(a) to 1(d) show steps of the LIGA process in which reference numeral 1 denotes a metallic substrate, reference numeral 2 denotes a PMMA (polymethyl methacrylate) resist film coated thickly on the metallic substrate 1, reference numeral 3 denotes a masking substrate, reference numeral 4 denotes a masking pattern, reference numeral 5 denotes synchrotron radiation and reference numeral 6 denotes electroformed nickel. The synchrotron radiation 5 is emitted by a synchrotron (not shown) and is a powerful X-ray whose beam has a narrow spread. In the known LIGA process, a microscopic metallic member is produced in the following steps (a) to (d) corresponding to FIGS. (a) to 1(d), respectively.
(a) The PMMA resist film 2 is deeply exposed through the masking pattern 4 by the synchrotron radiation 5 as shown by the broken lines in FIG. 1(a).
(b) The exposed portions of the PMMA resist film 2 are removed by development such that cavities are formed in the PMMA resist film 2 as shown in FIG. 1(b).
(c) Nickel 6 is filled in the cavities of the PMMA resist film 2 by electroforming as shown in FIG. 1(c).
(d) The PMMA resist film 2 is removed and thus, the electroformed nickel 6 remains on the metallic substrate 1 as shown in FIG. 1(d).
In the above known method, it is possible to obtain a microscopic metallic structure having a high aspect ratio but its cross-sectional shape is restricted to a rectangular shape formed by parallel lines defined by the synchrotron radiation. Therefore, the known method has such a drawback that since three-dimensional shape of the structure is limited, a structure having an arbitrary three-dimensional shape cannot be obtained, thus resulting in lack of versatility in use.